Sometimes wisdom comes from the most unexpected of sources. Earlier this week my car died while commuting over the Hollywood freeway, necessitating the help of a flatbed tow truck. The middle aged Guatemalan tow truck driver ended up imparting a helpful natural garden solution that discourages creatures from prowling into the backyard at night and also leaving "presents". He had trouble with cats using his backyard as a feline outhouse, but didn't want to capture or hurt them. Instead, he recommended the use of ground cinnamon; he advised purchasing it in bulk at discount groceries like Costco or latin markets that sell the spice in large amounts. Apparently cats dislike the smell and just mosey along, looking for more agreeable pastures; he hasn't had any problems since sprinkling it around the borders and corners of his garden.
I might give this a try, since our apartment's front yard has become my neighbor's cat's "spot" for doing her thing, and it's not too fun cleaning the garden with these little presents from our otherwise pleasant whiskered friend, Inga. Knowing how resourceful she is, I wouldn't be surprised if she just got some eggs, flour and sugar and baked me some cat litter cookies.